A VHDL based interpolator and base line restorer for a brain-PET scanner

This work is part of a large project contributing in the design and development of medium field and high resolution Positron Emission Topographic (PET) scanners. The Multi Pixel Photon Counters (MPPCs) are an elementary part of each PET scanner. They convert the scintillation energy, originated by the emitted gamma rays from patient's body, into an electrical pulse. These pulses are later on conditioned and processed to locate the cancerous cells in the patient's body. The form of these pulses is very important in making a precise localization of the cancerous cells. However, the acquisition chains of these pulses add specific artifacts in them like offsets, attenuations, etc. Moreover, the Analog to Digital conversion module limits the digital signal temporal resolution. Collectively, these artifacts effect the system precision in terms of measuring the depth of interaction and the time stamp. It renders a reduction in the system sensitivity and resolution. In order to overcome these inadequacies a digital baseline restorer and an interpolation modules are devised. They respectively compensate artifacts of the signal offset and of the signal temporal resolution limitation. These modules are implemented in VHSIC Hardware Description Language (VHDL). The functionality of implemented modules is tested with functional simulations. Results are presented, which assure a proper operation of the developed modules.